Refrigeration apparatus with defrost means



Ju 1968 E. H. FROHBIETER REFRIGERATION APPARATUS WITH DEFROST MEANS Filed Sept. 1, 1966 2 Sheets-Sheet l FIG.2

INVENTOR. EDWIN H. FROHBI ETER June 1963 E. H. FROHBIETER REFRIGERATION APPARATUS WITH DEFROST MEANS 2 Sheets-Sheet z Filed Sept.

INVENTOR EDWIN H. FROHBIETE 1 By 4 e4 FIGS) Unitcd States Patent 3,387,463 REFRIGERATION APPARATUS WITH DEFROST MEANS Edwin H. Frohbieter, Stevensville, Mich., assignor to Whirlpool Corporation, a corporation of Delaware Filed Sept. 1, 1966, Ser. No. 576,636 16 Claims. (Cl. 62-140) This invention relates to refrigeration apparatus and in particular to control means for use in refrigeration apparatus.

In one form of refrigeration apparatus, chilled air is delivered to a compartment through a duct by means of suitable air translation means. The air is chilled by being passed in heat transfer association with a suitable chilling means prior to its delivery to the compartment. A problem arises in the conventional refrigeration apparatus of this type in that the moisture in the air being chilled by the chilling means becomes deposited on the chilling means in the form of frost and when the frost deposit builds up sufficiently undesirably impedes, and in some cases blocks off, the flow of the air through the system.

A number of controls for effecting an automatic defrosting of the frosted chilling means heretofore have been employed in the refrigeration art. The present invention comprehends an improved control means for controlling the operation of the chilling means and for effecting sucha defrosting operation in response to frost build up on the chilling means.

Thus, a principal feature of the present invention is the provision of a refrigeration apparatus having new and improved control means.

Another feature of the invention is the provision of such refrigeration apparatus having new and improved means for controlling the operation of the air chilling means thereof.

Still another feature of the invention is the provision of a refrigeration apparatus having a new and improved means for tempering the chilled air delivered to the compartrnent by recirculating a portion of the air from the compartment into a chilled air, delivery duct for mixing with the chilled air downstream of the air translating means.

A further feature of the invention is the provision of such refrigeration apparatus having new and improved means for controlling a defrost operation thereof.

Still another feature of the invention is the provision of such refrigeration apparatus having new and improved means for controlling the operation thereof including means defining a passage between the compartment to be refrigerated and the duct for delivering chilled air to the compartment and provided with means responsive to the condition of air in the passage for controlling operation of the apparatus.

A still further feature of the invention is the provision of such refrigeration apparatus having new and improved means responsive to the temperature of the air in said passage foreffecting control of the apparatus.

Yet another feature of the invention is the provision of such refrigeration apparatus wherein the passage is arranged to have alternative air fiow theretnrough from the compartment into the duct and from the duct into the compartment as a function of the air delivery conditions in the duct.

Another feature of the invention is the provision of such refrigeration apparatus having new and improved electrical circuitry for control thereof.

Still another feature of the invention is the provision of such refrigeration apparatus having new and improved safety control means.

3,387,453 Patented June 11, 1968 ice A further feature of the invention is the provision of such refrigeration apparatus having new and improved means for preventing reoperation of the air chilling means until it reaches a preselected high temperature.

Another feature of the invention is the provision of such refrigeration apparatus having new and improved means for preventing reoperation of the air chilling means until substantially all melt produced in the defrosting thereof is directed to the disposal means.

Other features and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawing wherein:

FIGURE 1 is a front elevation of a refrigeration apparatus embodying the invention with certain parts omitted for clarity;

FIGURE 2 is a vertical section thereof taken substantially along the line 2-2 of FIGURE 1;

FIGURE 3 is a front elevation of a modified form of refrigeration apparatus embodying the invention with certain parts omitted for clarity;

FIGURE 4 is an enlarged horizontal section taken substantially along the line 44 of FIGURE 1;

FIGURE 5 is a fragmentary vertical section taken substantially along the line 5-5 of FIGURE 4;

FIGURE 6 is a fragmentary enlarged front elevation of the apparatus of FIGURE 1 illustrating in greater cletail the air flow sensing means;

FIGURE 7 is a fragmentary horizontal section taken substantially along the line 77 of FIGURE 6;

FIGURE 8 is a schematic wiring diagram of the electrical circuitry of the refrigeration apparatus embodying the invention; and

FIGURE 9 is a schematic wiring diagram of another form of electrical circuitry of the refrigeration apparatus embodying the invention.

In the exemplary embodiment of the invention as disclosed in FIGURES l, 2 and 4 through 8, a refrigeration apparatus generally designated 10 is shown to cornprise a cabinet 11 defining a plurality of compartments to be refrigerated, herein more specifically illustrated as an upper refrigerator compartment 12 and a lower freezer compartment 13. Doors (not shown) are provided to close the compartments. Refrigeration of the compartments 12 and 13 is herein effected by delivering chilled air through a duct 14 having a first outlet 15 into the refrigerator compartment 12 and a second outlet 16 into the freezer compartment 13. The air is forced through the duct 14 by suitable air translating, or moving, means such as blower 17 which may be driven by a suitable electric motor 18, as best seen in FIGURE 4.

The air so moved by blower 17 is chilled by a heat transfer device, such as evaporator 19, which may be of conventional construction having a plurality of fins 20 defining therebetween a plurality of passages 21. The chilled air is returned from compartment 12 through a return duct 22 having an inlet 23 in the lower portion of compartment 12, and the chilled air is returned from compartment 13 through a return duct 24 having an inlet 25 in the lower portion thereof.

The refrigeration apparatus may further include a conventional compressor 26 and condenser 27 with a fan 28 being also driven by motor 18 for flowing room air past the compressor and condenser in a conventional manner. As shown in FIGURE 5, the cabinet 11 may further define a lower apparatus space 29 in which the evaporator 19, blower 17, fan 28, compressor 26 and condenser 27 may be installed.

In normal operation, humidity in the air flowed through the evaporator passages 21 deposits on the evaporator in the form of frost. When this frost builds up sufficiently to substantially impede the flow of the air through the passages 21, it is desirable to discontinue the air chilling operation and to initiate a defrosting operation wherein heat is applied to the frost, causing it to melt from the evaporator. As shown in FIGURE 5, a drain tube 30 is provided for delivering the melt from the evaporator to a suitable drain pan 31.

The present invention, as indicated briefly above, is concerned with the control of the refrigeration apparatus to initiate a defrosting operation automatically when the impediment to the air flow through the evaporator reaches a preselected level. To this end, means are provided for sensing the condition of chilled air fiow through the duct 14 in a novel manner. More specifically, as shown in FIG- URES 1 and 6, communication between compartment 12 and the duct 14 is provided at a location 32 spaced below the outlet 15. The duct 14 is constricted adjacent location 32 to define a venturi portion 33. A pair of passages 34 and 35 are provided through a compartment liner 36 communicating with duct portion 32 at opposite sides of the duct. Thus, chilled air flowing upwardly through duct 14 to outlet 15 normally draws air from compartment 12 into the duct through the passages 34 and 35 by an air entraining venturi action to cause recirculation of a portion of the compartment 12 air which mixes with the colder air in duct 14, thereby tempering the air entering the compart-ment from outlet 15. In addition, the recirculated air adds to the volume of air being delivered to compartment 12 through outlet 15. This tends to create a relatively greater amount of air movement in compartment 12, which alleviates stratification that sometimes occurs in refrigerator compartments. A thermostat 37 is disposed in one of the passages, herein passage 35, for sensing the temperature of the air flowing through that passage. In normal operation when the air is being drawn from the compartment 12 into duct 14, the air is relatively warm, for example at 34 F., as compared to the chilled air in duct 14, for example at -10 F., and thermostat 37 is arranged to permit normal cycling of the refrigeration apparatus as hereinafter described.

When, however, frost builds up in the passages 21 of evaporator 19 to substantially block flow of the air therethrough, the flow of chilled air upwardly through duct 14 is decreased until the pressure of the air at position 32 is insufiicient to raise the column of cold air in duct portion 38 to discharge it through outlet 15. At this time, the relatively cold air at position 32 in the duct 14 will tend to flow through passages 34 and 35 into the warmer air in compartment 12. The thermostat 37 senses the low temperature of this chilled air flowing therepast in passage 35 and in response thereto provides a signal to discontinue operation of the apparatus 10 providing chilled air to the duct 14 and further initiate operation of the apparatus to effect a defrosting of the evaporator.

The above described reversal of air fiow direction through passages 34 and 35 is caused by a difference in density between the relatively cold air within duct 14 and the warmer air within compartment 12. The colder air within portion 38 of duct 14 and above passages 34 and 35, being denser, will under static conditions, tend to flow by gravity through passages 34 and 35 to displace the warmer air within compartment 12. However, with the blower of the system in operation, a dynamic or velocity pressure is imposed on the cold air in portion 38 of duct 14, which pressure is great enough to overcome the static tendency of the cold air to displace the warmer air within compartment 12.

When the evaporator begins to frost, the volume of air which the air translation means is capable of moving past the evaporator is diminished. The diminishing air flow past the evaporator results in a reduction of dynamic or velocity pressure within duct 14. The system may be balanced so that upon reaching a predetermined frost condition on the evaporator, the dynamic forces acting on the column of air in duct portion 38 will no longer be suflicient to raise that column of air. Then the air moving in duct 14 will seek a new flow path, namely from duct 14, through passages 34 and 35 and into compartment 12. The length of the portion 38 of duct 14 is selected so that the reversal of air flow through passages 34 and 35 takes place when the evaporator has become undesirably blocked.

The defrosting of the evaporator may be effected by a heater 39 disposed in thermal transfer association with the evaporator 19, although as will be obvious to those skilled in the art other suitable means for effecting defrosting of the evaporator may be employed. A control circuit associating the thermostat 37 with the heater 39 is illustrated in FIGURE 8. As shown in FIGURE 8, the blower motor 18 and compressor 26 are connected in parallel to one power supply lead L through a conventional thermostat switch 40 which may be mounted in compartment 12 in the conventional manner for controlling the temperature thereof. The other side of the paralleled motor 18 and compressor 26 is connected to the other power supply lead L through a single pole, double throw relay switch 41 having a fixed contact 41a connected to the blower motor 18 and compressor 26 and a moving contact 41!) connected to power supply lead L The switch 41 is operated by a suitable electromagnetic coil 410 which is connected to a second fixed contact 41d of switch 41 in series with heater 39, and a normally closed thermally responsive switch 42 disposed in the evaporator 19 which is arranged to open at a predetermined high temperature in the evaporator, such as 55 F. Thermostat 37 comprises a thermally responsive switch means arranged to close at a predetermined temperature such as 20 F., and may comprise a conventional bimetallic switch connected between moving contact 41b of relay switch 41 and power supply lead L through a reset heater 43 and thermally responsive switch 42. The heater 43 when energized provides heat to the thermostat 37. A normally open thermally responsive switch 44 mounted on evaporator 19, which closes in response to a predetermined low temperature such as -40 F., is connected in parallel with switch 37 to power supply lead L The operation of apparatus 10 with the control arranged as shown in FIGURE 8 is as follows. In normal operation, the compressor 26 and blower motor 18 are energized periodically under the control of the thermostat switch 40 so as to maintain the temperature in the refrigerator chamber 12 at a preselected temperature such as 34 F. When, however, frost accumulates on the evaporator fins 20 so as to effectively block air flow therethrough, thermostat switch 37 closes as a result of the above described flow of the relatively cold air at a temperature such as 10 F. in duct 14 through the passage 35 in heat transfer association with the thermostat switch 37. Thus, a circuit is completed from power supply lead L through the closed switch 37 and through relay coil 41c and heater 39 to the other power supply lead L through closed thermostat switch 42. Energization of coil 41c causes moving contact 41b of relay switch 41 to be thrown from fixed contact 41a to fixed contact 41d, thereby discontinuing operation of the blower motor 18 and compressor 26, and maintaining energization of the coil 41c to hold the relay switch 41 in the thrown position notwithstanding a subsequent opening of the switch 37 The heater 43 is currently energized to reopen switch 37 and thereby establish the control for a subsequent cycle of operation. Coil 41c remains energized until thermostat switch 42 opens at the relatively high temperature indicating a completion of the defrosting operation. Deenergization of coil 410 by the opening of switch 42 permits relay switch 41 to return to the normal position of FIGURE 8, reestablishing the normal circuit through the blower motor 18 and compressor 26 under the control of cabinet thermostat 40. Switch 44 is provided to initiate the above described defrost cycle in the event thermostat switch 3'7 fails to close and, thus, functions as a safety switch.

Referring to FIGURE 9, another illustrative circuit for controlling the paralleled blower motor 18 and compressor 26 is shown to include a double throw thermostat switch 137 in lieu of the single throw switch 37. As shown in FIGURE 9, a moving contact 1370 of the switch 137 is connected to one power supply lead L and is selectively closable with a first fixed contact 137b in turn connected to a moving contact 144a of a double throw safety switch 144, and a second fixed contact 1370 connected to series related evaporator heater 39 and thermostat switch 42. The reset heater 143 is also connected between fixed contact 137c and power supply lead L Moving contact 144a of switch 144 is selectively engageable with a first fixed contact 14411 thereof connectcd to one side of the paralleled blower motor 118 and compressor 126, and with a second fixed contact 144a connected to fixed contact 137a of switch 137.

Where the control of the apparatus is as shown in FIGURE 9, the operation is as follows. Switch 137 is normally in engagement with fixed contact 137b, as shown in FIGURE 9, as long as the air flow through duct 14 is upwardly therethrough to the outlet 15. When a reversal of the air fiow, however, occurs as discussed above, the switch 137 is thrown so as to have movable contact 137a become spaced from fixed contact 13712 and engage fixed contact 137a. This breaks the circuit to the blower fan 118 and compressor 126 so that further operation thereof is prevented until the defrosting cycle is completed. Power is supplied at this time from power supply lead L through the switch 137 to the heater 139 which remains energized until the switch 42 opens when the evaporator reaches the relatively high temperature indicating a complete defrosting thereof such as 55 F., as indicated above. The heater 143 in parallel with heater 139 provides heat to the switch 137 and is selected so that the switch 137 will reset itself in the condition of FIGURE 9 only after the defrost cycle is terminated by the opening of switch 42. Thus, a period of time is provided during which the melt may be conducted from the evaporator 19 before operation of the compressor 126 is recommenced. The safety switch 14-4 preferably has a reset temperature similar to that of the switch 137.

The invention has been disclosed above in connection with a two compartment refrigeration apparatus. The invention may similarly be employed with a single compartment apparatus such as vertical freezer apparatus 210, as shown in FIGURE 3, wherein the passages 234 and 235 are provided adjacent the bottom of the single compartment 212. In this embodiment, the length of the duct portion 238 above the duct portion 232 is of subsfantially greater length than that of the duct portion 38 of apparatus 18 because in the freezer the temperature differential between the air in compartment 213 and duct 214 is less. In the vertical freezer, the temperature of the compartment air may be for example 0 F., with the temperature of the air in duct 214 at, for example F. Thus, the difference in density between the compart ment air and the duct air is less and the static tendency of the duct air to displace compartment air is less. To compensate for the lesser tendency to displace, the column of air in duct 214 above portion 232 is lengthened. Thus, the reversal of air flow through passages 234 and 235 may be preselected to take place at approximately the same frost build-up condition on the evaporator. While the lengthened column of air in the freezer duct is preferred, it is possible to use the same duct length as in the refrigerator since the invention resides not in the exact length of the duct but rather in there being a portion of ducting above the passages 234 and 235.

The same electrical circuits as used with the refrigerator apparatus may be used with the freezer. However, the operating temperatures of the thermostats 237 and 240 must be selected to reflect the lower compartment temperature within the freezer.

Thus, the present invention comprehends an improved refrigeration apparatus wherein chilled air delivered to a compartment is tempered by the delivery thereinto of a portion of the air in the compartment of a venturi action in the duct delivering the chilled air to the compartment. Means are provided for sensing the direction of the air flow through the recirculation passage for providing an improved control of the operation of the refrigeration apparatus. In the present disclosed embodiments of the invention, the reversal of the air flow direction in the recirculation passages may be sensed by a thermally responsive sensing means since air flowing through the duct from the compartment into the duct is at the relativly high compartment temperature compared to the temperature of the chilled air normally flowing from the duct into the compartment through the outlet 15. As disclosed above, the invention further comprehends an improved circuit arrangement for utilizing the signal provided by the sensing means to provide improved automatic defrosting control of the refrigeration apparatus.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a refrigeration apparatus;

means for chilling air;

cabinet means defining a compartment to be refrigerated',

duct means having a venturi portion and an outlet open ing into said compartment for conducting chilled air from said chilling means through said outlet into said compartment;

air translation means upstream of said outlet for flowing chilled air from said chilling means through said duct means into said compartment; and

means defining a passage between said compartment and said duct means venturi portion and downstream of said air translation means for permitting air flowing through said duct means and outlet to draw air by venturi action from said compartment into said duct means to mix with said chilled air therein for subsequent discharge of the mixed air through said outict into said compartment.

2. In a refrigeration apparatus:

means for chilling air;

cabinet means defining a compartment to be refri crated; duct means having an outlet opening into said compartment for conducting chilled air from said chilling means through said outlet into said compartment;

air t anslation means for flowing chilled air from said chilling means through said duct means into said compartment;

means defining a passage between said compartment and said duct means spaced from said outlet for permit- 'ng air flowing through said duct means and outlet to draw air from said compartment into said duct means to mix with said chilled air therein for subsequent discharge of the mixed air through said outlet into said compartment; and

control means including means in said passage responsive to a condition of the air therein for controlling operation of said chilling means to discontinue air chilling operation thereof.

3. The refrigeration apparatus of claim 2 wherein said last-named means is arranged to be responsive to a reversal of air flow from said duct means through said passage defining means to said compartment.

4. The refrigeration apparatus of claim 2 wherein said last-named means comprises a thermally responsive device.

5. The refrigeration apparatus of claim 2 wherein said outlet is disposed above the level of said passage defining means whereby a body of air is disposed in said duct means above said passage defining means for causing chilled air to be diverted outwardly through said passage when the pressure of said flowed air is below that necessary to move said body of air upwardly and outwardly through said outlet.

6. The refrigeration apparatus of claim 2 wherein said control means further includes means for discontinuing air chilling operation of said chilling means at a preselected low temperature in the event said means in said passage fails to discontinue said air chilling operation responsive to said condition.

7. The refrigeration apparatus of claim 2 wherein said air chilling means includes a heat transfer means having a pair of spaced heat absorbing portions, said air translation means flOWs air through the space between said portions for chilling the air, and said air condition responsive means is responsive to a condition of air flow through said means defining a passage resulting from a restriction in the air flow through said space due to frost build-up on said portions of the heat transfer means impeding the air flow through said space.

8. The refrigeration apparatus of claim 7 further including means actuatable by said air condition responsive means for defrosting said heat transfer means.

9. The refrigeration apparatus of claim 2 wherein said control means includes a relay having a coil and a first double throw switch operable by said coil, said air condition responsive means includes a second switch connected in series with said coil for energizing said coil when said air fiow condition occurs, and said air chilling means includes electrically operable means connected to said first switch to be energized therethrough when said first switch is in one thrown condition and to be de-energized when said first switch is in the other thrown condition thereof.

10. The refrigeration apparatus of claim 9 wherein said first switch shunts said second switch when said first switch is in said other thrown condition thereof.

11. The refrigeration apparatus of claim 9 including electrically operable means for defrosting said air chilling means connected to said first switch to be energized when said first switch is in said other thrown condition.

12. The refrigeration apparatus of claim 2 wherein said air chilling means comprises electrically operable means, said air condition responsive means include switch means connected in series with said electrically operable air chilling means and arranged to de-energize said electrically operable air chilling means when said air flow condition occurs.

13. The refrigeration apparatus of claim 12 further including electrically operable means for defrosting said air chilling means and said switch means being further connected in series with said defrosting means and arranged to energize said defrosting means when said switch means is arranged to de-energize said electrically operable chilling means.

14-. The refrigeration apparatus of claim 2 wherein the control means further includes means for preventing reoperation of said chilling means after discontinuation of operation thereof until said air chilling means reaches a preselected high temperature.

15. The refrigeration apparatus of claim 2 wherein means are provided for defrosting the air chilling means and directing melt arising from said defrosting to a disposal means, and said control means further includes means for preventing reoperation of said chilling means after discontinuation of operation thereof until substantially all said melt is directed to said disposal means.

16. In a forced air refrigeration apparatus having a food storage compartment to be maintained at a first temperature, air Chilling means for chilling air to below freezing temperatures lower than said first temperature, and air moving means for moving air from said air chilling means to said food storage compartment, the improvement comprising: duct means for providing fluid communication between said air chilling means and said food storage compartment, said duct means including an outlet portion for delivering air to said food storage compartment, an air entraining portion spaced from said outlet portion for drawing air from said food storage compartment into said duct means, and a connecting portion for connecting said outlet portion and said air entraining portion, said connecting portion being at least partially above the level of said air entraining portion whereby during operation of said refrigeration apparatus said air moving means moves a desired predetermined volume of air to said food storage compartment from said air chilling means, and air from said food storage compartment is entrained with the air from said air chilling means and mixed therewith prior to delivery from said outlet portion, but when the volume of air moved by said air moving means is reduced below a predetermined volume due to frost build-up on said air chilling means the air moved by said air moving means is caused to flow from said duct means through said air entraining portion into said food storage compartment.

References Cited UNITED STATES PATENTS 2,152,291 3/1939 Starr 62-419 XR 2,889,692 6/1959 MCGIEW 62-419 XR 3,243,972 4/1966 Wiese 62419 XR 3,321,933 5/1967 Scheitlin 62419 MEYER PERLIN, Primary Examiner. 

1. IN A REFRIGERATION APPARATUS; MEANS FOR CHILLING AIR; CABINET MEANS DEFINING A COMPARTMENT TO BE REFRIGERATED; DUCT MEANS HAVING A VENTURI PORTION AND AN OUTLET OPEN ING INTO SAID COMPARTMENT FOR CONDUCTING CHILLED AIR FROM SAID CHILLING MEANS THROUGH SAID OUTLET INTO SAID COMPARTMENT; AIR TRANSLATION MEANS UPSTREAM OF SAID OUTLET FOR FLOWING CHILLED AIR FROM SAID CHILLING MEANS THROUGH SAID DUCT MEANS INTO SAID COMPARTMENT; AND MEANS DEFINING A PASSAGE BETWEEN SAID COMPARTMENT AND SAID DUCT MEANS VENTURI PORTION AND DOWNSTREAM OF SAID AIR TRANSLATION MEANS FOR PERMITTING AIR FLOWING THROUGH SAID DUCT MEANS AND OUTLET TO DRAW AIR BY VENTURI ACTION FROM SAID COMPARTMENT INTO SAID DUCT MEANS TO MIX WITH SAID CHILLED AIR THEREIN FOR SUBSEQUENT DISCHARGE OF THE MIXED AIR THROUGH SAID OUTLET INTO SAID COMPARTMENT. 